Decrease In Tensile Properties Research Articles

Age-related changes in the tensile properties of human articular cartilage: a comparative study between the femoral head of the hip joint and the talus of the ankle joint

Specimens of articular cartilage from the superficial and mid-depth zones of the human femoral head and the talus of the ankle joint were tested in tension in planes parallel to the articular surface and parallel to the predominant orientation of the superficial collagen fibrils. The tensile fracture stress of cartilage from both the superficial and mid-depth zones of the femoral head decreases considerably with age. The superficial zone decreased from 33 MPa at 7 years to 10 MPa by the age of 90 years, while the mid-depth zone decreased from 32 MPa at 7 years to 2 MPa by the age of 85 years. In contrast the fracture stress of both levels of cartilage from the talus of the ankle did not decrease significantly with increasing age. The tensile stiffness at 10 MPa of both the superficial and mid-depth zones of the femoral head decreased with age. That of the superficial zone decreased from 150 MPa at 7 years to 80 MPa at 90 years, while the mid-depth zone decreased from 60 MPa at 7 years to 10 MPa at 60 years. The stiffness of talar cartilage from the superficial zone decreased by 20%, while that of the mid-depth zone showed a slight increase in stiffness at 10 MPa with increasing age. There was no significant decrease in the tensile stiffness at 1 MPa with age for either the femoral head or talar cartilage. Based on the results of previous studies it is possible to conclude that the decrease in tensile properties seen in the femoral head results from a deterioration in the tensile properties of the network of collagen fibrils. It is suggested that progressive fatigue failure, perhaps with associated changes in the structure of cartilage due to altered chondrocyte metabolism, causes the reduction in tensile properties with age. The results offer a potential explanation for the observation that osteoarthritis commonly occurs in the hip and knee joints at an increasing incidence as age increases, while the condition only rarely occurs in the ankle joint except as a secondary event to trauma.

Thermal fatigue of Ti-24Ai-11NB/SCS-6

The effect of thermally cycling in air with no applied load was studied using the Ti-24A1-11Nb (atomic percent)/SCS-6 composite system. Mechanisms of damage determination were observable cracking and residual tensile properties. Either the number of cycles or the temperature range was varied from specimen to specimen. Effects of number of cycles were investigated using a temperature range of 150 °C to 815 °C. Comparisons of temperature range effects were made at a constant cycle count of 500. Matrix cracking was observed at a †T of 450 °C and greater when oxidation was significant. Transverse cracking was not observed in specimens that were cycled to maximum temperatures where oxidation was insignificant, even for †T's as large as 500 °C. A decrease in tensile properties coincided with the observed transverse matrix cracking.

Effect of heat treatment on nylon‐6 tire cords

AbstractThe behavior of nylon‐6 tire cords at elevated temperature has been evaluated. The heat treatment of cords at 200°C for 16 h was found to reduce their tensile properties considerably. This has been attributed to the decrease in average molecular weight and change in molecular weight distribution as ascertained by fractionation studies. Heat setting of cords in the temperature range of 180–210°C without any applied tension showed some decrease in tensile properties. This has been ascribed to the higher degree of shrinkage of the cords and hence increased chain folding in the molecular structure. However, irrespective of time and temperature of heat treatment, shrinkage was reduced with increasing tension on the cord. Effect of heat setting on density and crystallinity was also evaluated.

Effects of Cathode-Mandrel Surface Irregularities on the Mechanical Properties and Structure of Electroformed Iron Foil

Iron foil, of thicknesses between 003 and 0.15 mm has been electroformed at a current density of 30 A/dm2 and an electrolyte temperature of 100°C upon cathodes of surface roughness ranging from 0.04 to 4.4 μm Ra. The surface roughnesses of the face of the foil formed adjacent to the cathode, and of that electrode, are similar. The roughness of the reverse anodic face increases with increasing foil thickness, due to the increase in size of the crystal growth sites. The hardness of the cathodic face of the foil is unaffected by either cathode surface roughness or foil thickness. The hardness of the anodic face increases with both increasing cathode surface roughness and decreasing foil thickness, due to corresponding changes in grain size. A slight net decrease in tensile properties with increasing cathode surface roughness is attributed to the greater amount of stress concentration borne by the rougher foils. Young's modulus for the foil is not affected by cathode surface roughness. The electroforming of foil upon a mandrel surface carrying an isolated V-shaped scratch, 0.14 mm deep and 0.28 mm wide, has also been studied by numerical and experimental methods. The cathodic surface of foil is found to adopt the shape of the scratch whilst its upper side becomes level. The effect upon the geometric configuration of the foil depends upon the relationship between current efficiency and current density for the electrolyte, and on the polarisation (overpotential) characteristics at the mandrel surface.

SURFACE ULTRASTRUCTURE AND TENSILE PROPERTIES OF CATHEPSIN AND COLLAGENASE TREATED MUSCLE FIBERS

Beef and rabbit psoas muscle fibers were soaked in a crude muscle cathepsin preparation, collagenase or 2% KCl. Tensile properties (breaking strength and break elongation) and surface ultrastructure were monitored. Cathepsins considerably accelerated decreases in tensile properties found in an un‐soaked control while KC1 produced significant but less extreme effects. Collagenase showed similar results for breaking strength but break elongation was only slightly influenced. Surface ultrastructure revealed that KC1 caused a variable loss of structure including collapse and disappearance of striations, swelling and some transverse fiber breakage. Cathepsins speeded and expanded this damage producing multiple breakage with extensive disruption in some cases. These effects are similar to those observed in naturally aged meat and occur at the same temperature and pH. Collagenase treatment, however, initially brought about a shredding and dissolution of collagen fibers followed by disintegration of the sarcolemma and exposure of relatively undamaged myofibrils.

Studies on corrosion of aluminum alloy welds

The corrosion tests of TIG-welds in 1080, 5052, 5083-O, H plates, 6061 and AlZnMg-T4, T6 plates were made for a period of one year in industrial and marine atmospheres and in industrial and sea waters.The results obtained were summarized as follows:(1) Many small pits were produced on the whole surface of all specimens corroded in industrial and marine atmospheres. There were no differences to be observed among the all kinds of materials.(2) In industrial and sea waters, 1080, 5052 and 5083 alloy welds had high corrosion resistivity, while 6061 and AlZnMg alloy welds were severely corroded in their heat-affected zones.(3) The decreases in tensile properties of welds by corrosion were negligibly small, except the AlZnMg alloys corroded in industrial water.(4) In industrial water, the solid solution zone of welded joints in AlZnMg-T6 specimens and all parts of T 4 specimens, except for weld metal, were severely corroded.(5) Intergranular corrosion was found in the fusion zone and solid solution zone of welds in heat-treating alloys such as 6061 and AlZnMg.

A STUDY ON CORROSION AND ITS PROTECTION OF ALUMINIUM ALLOYS IN CONTACT WITH DISSMILAR METALS

Several methods of protection of aluminium alloys to corrosion in contact with diss milar metals, that is inserting of zine plate, cadmium plate and calking paste, are compared about their effect combined to the painting.Tests were carried out in respect to the change of appearance and the decrease of tensile properties of aluminium alloys after corrosion in 5.85%NaCl + 0.3%H2O2 solution for 1 month and 3 months. To the panel plate of 52S-O or ND-O one band of mild steel or brass was attached by means of mild steel r vets. Many combinations of vehicles and pigments as calkcng paste were compared on the effect of protection from contact corrosion, resulting that the paste of alkyd resin containing aluminium powder, zinc powder and zinc-chromate were proved to be the most effective. After this, when aluminium alloy plate is not painted, inserting of zinc plate is the most effective, while the consumption of zinc is comparatively large. When aluminium alloy plate is painted, inserting zinc plate unfavourably destroies the paintcoats. So the calking of paste between aluminum and dissimilar metal band before finish painting is the best.